Mobile cranes are often employed for several lift jobs at a single construction site (for example, a chemical plant). For each job, the crane has to be moved to a new location and prepared for the new job. Typically, the crane has to be moved several tens or hundreds of meters.
A disadvantage of prior art mobile cranes relates to the practice described above, wherein the crane is moved from one location to the next. With most prior art cranes, additional cranes and transport vehicles are needed in order to move the superlift ballast to the new location. The use of additional cranes and transport vehicles is time consuming and poses additional safety hazards to personnel.
In some examples of the prior art, the superlift ballast is mounted on a separate wheeled ballast car attached to the superstructure, having steerable wheels driven by associated drive means. The problem is that this construction requires an extraordinary robust and expensive ballast car, which undesirably increases the costs of the crane. In another example, a mobile crane has a ballast car attached to the superstructure by a telescopic beam. Like the first example, this construction also has steerable wheels, resulting in an undesirable complex and costly ballast arrangement.
As another example, the Demag CC 8800 crane has a superlift ballast car (max 600 ton) attached to the base structure via a telescopic beam. This crane further has a superstructure ballast mounted on the rear end of the superstructure. For further stabilizing, the Demag CC 8800 crane uses a “central ballast” (max 100 ton) on the chassis of the base structure. This “central ballast” construction is done by providing the front and rear beam of the base structure with a centrally arranged support platform on which metal ballast plates can be stacked.
As another example of prior art, a crane is not provided with a superstructure ballast. Rather, the crane has a horizontal beam attached to the superstructure, wherein the horizontal beam carries the superlift ballast.
A need exists to provide an improved mobile crane, having provisions for handling the superlift ballast, which allows for a more efficient use of the crane at affordable costs.
The embodiments meet these needs.
The embodiments are detailed below with reference to the listed Figures.